Thujene (or α-thujene) is a natural organic compound classified as a monoterpene. It is found in the essential oils of a variety of plants, and contributes pungency to the flavor of some herbs such as Summer savory. The term thujene usually refers to α-thujene.

2-Methylnaphthalene is a polycyclic aromatic hydrocarbon (PAH). On February 22, 2014, NASA announced a greatly upgraded database for detecting and monitoring PAHs, including 2-methylnaphthalene, in the universe. According to NASA scientists, over 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life.

Cadalene or cadalin (4-isopropyl-1,6-dimethylnaphthalene) is a polycyclic aromatic hydrocarbon with a chemical formula C15H18 and a cadinane skeleton. It is derived from generic sesquiterpenes, and ubiquitous in essential oils of many higher plants. Cadalene, together with retene, simonellite and ip-iHMN, is a biomarker of higher plants, which makes it useful for paleobotanic analysis of rock sediments.

1-Methylnaphthalene is a polycyclic aromatic hydrocarbon (PAH). It has a cetane number of zero, and was previously used as the lower reference for cetane number. However, due to the expense and handling difficulty of 1-methylnaphthalene, it was replaced in this capacity by isocetane, with a CN of 15.